Legislators and supporters cheer after Gov. Peter Shumlin signed a bill into law Thursday outside the State House that requires the labeling of GMO ingredients in many foods. It is the first law of its kind in the nation to pass without so-called trigger clauses.

MONTPELIER — Before a cheering crowd of hundreds, Gov. Peter Shumlin signed into law a first-of-its-kind food labeling bill, even as Vermont food producers continued to voice their opposition.

The State House lawn was filled with families and consumer advocates Thursday afternoon as Shumlin signed the legislation that will require the packaging of some foods to indicate if they contain genetically modified organisms, or GMOs.

“We will sign the first bill in America, joining 60 other countries, where Vermonters will have the right to know what’s in their food,” said Shumlin, who compared the action to Vermont being the first state to abolish slavery and to allow civil unions.

The law will require the labeling of many types of food, from bread to produce, while containing exemptions for meat and dairy products.

Parties on both sides of the debate acknowledge the new state law, which runs counter to the labeling laws under the federal Food and Drug Administration, is likely to be challenged in court.

“There are some who have said that there are forces in this country in the food business who don’t want Vermonters to have this right and that they might use that other branch of government to try and deny us that right,” Shumlin said.

In anticipation of lawsuits — and as a way for supporters of the law to put their money where their mouths are — the state has launched a Kickstarter-style fundraising campaign at www.foodfightfundvt.org.

“We are asking people all across America and all across the great state of Vermont to go to (the website) and make a donation so that we can win the Vermont Food Fight Fund fight, not only for Vermont, but for America,” Shumlin said. The governor signed the bill while sitting in the chair used by corporate representatives who testified against it, said Senate President Pro Tem John Campbell.

The law will be in effect after July 1, 2016. At least two other states have passed GMO labeling laws, but theirs will not kick in until certain conditions are met.

While supporters enjoyed free ice cream Thursday from Ben & Jerry’s while cheering speeches by the governor, senators and representatives, some in Vermont’s food production industry were less than thrilled.

“I think most of the general public is being duped, and I think there’s an effort to gain market share by promoting fear,” said Bill Rowell, who operates a 900-head dairy farm with his brother in Sheldon.

Rowell said with 3 trillion meals served across the globe containing GMOs — without conclusive documentation of any negative effects — there isn’t sufficient evidence that GMOs are bad.

“If you have a food that requires less resources and produces greater yield while there are more people to feed, why would you move away from that?” Rowell asked.

Cathy Bacon, who operates a 25,000-square-foot food packaging facility in Randolph that is certified as organic and GMO-free, also voiced opposition to the law.

“They have so pulled the wool over the eyes of any Vermonter who signed a petition by telling half-truths,” Bacon said. “If states are allowed to pass individual labeling laws that trump FDA laws, companies like mine stand to make millions. The people who won’t benefit will be the start-ups.”

For a start-up company, Bacon said, changing labels is a “nightmare” because it is an expense for which it likely hasn’t budgeted.

“It’s going to cost jobs. It’s going to hurt tourism. Is the Vermont Country Store going to have to label the penny candies in the jars as having GMOs?” Bacon asked. “I’m so tired of hearing that Vermonters have a right to know what’s in their food. If you want to know what’s in your food, buy organic. If you don’t know what’s in your food, don’t buy it.”